Storm water (also know as stormwater) and contaminants (i.e. gross particulate matter, sediment, oil, grease, hydrocarbons, heavy metals etc,) enters storm water drains via ‘pits’ also know as catch basins and stormwater inlets. It is desirable to retain these contaminants at the point of entry to the stormwater piping system and to periodically remove them to avoid blockage and contamination of the stormwater drainage system. A wide variety of filters have been developed for this purpose and a number of relevant prior patents are discussed below.
U.S. Pat. No. 122,209 describes a removable grate that is inserted into a storm water drain inlet to effectively capture gross solids and prevent ingress to the storm water system.
U.S. Pat. No. 143,774 describes a removable sediment receptacle and associated flared inlet acting as both a sediment filter and foul air trap.
U.S. Pat. No. 4,419,232 describes a frameless tapered filter bag insert for a storm water drain suspended above the sump floor.
U.S. Pat. No. 5,985,157 describes a filter device for removing suspended solids from storm water that includes a filter bag constrained within a rigid cage structure.
U.S. Pat. No. 6,149,803 describes a tapered storm water filter bag that is supported and shaped by an internal frame.
U.S. Pat. No. 6,551,023 describes a storm water filtration system utilising a support basket for the filter constructed of netting material, together with cables traversing the bottom of the basket in an x-shape.
U.S. Pat. No. 658,639 describes a receiving basin which includes a mesh receptacle that extends to the internal volume of a storm water inlet sump.
U.S. Pat. No. 7,201,843 describes a storm water filter bag that includes a rectangular collar as an inlet and a central tubular filter for capturing sediment.
The primary objectives of stormwater filter systems are:                to retain a large volume of contaminants, compared to the size and dimensions of a specific catchpit—high volume efficiency;        to maintain performance and, throughput of the catchpit during periods of high flow;        to provide dimensional stability such that the filter does not bulge and beyond the dimensions of the inlet preventing removal;        to be able to be easily removed for maintenance by hand, without the requirement for mechanical lifting or induction by vacuum truck        
Recent filter systems that utilise a filtration mesh/fabric body can be broadly categorized into two types:                Filters that are flexible and self-supporting        Filters that are flexible and supported by an external rigid cage.        
Filters that are flexible and self-supporting tend to be of much smaller volume than the pits into which they are fitted, due to the fact that unsupported flexible materials cannot provide dimensional stability. This has a detrimental effect on the volume of material that can be retained in the filter and maintenance requirements.
Filters that are supported by external rigid cages are provided with dimensional stability as the filter body cannot bulge or expand beyond the limits of the cage. However, these cages can add significantly to the mass of the filter apparatus and cannot be collapsed for transport or bespoke fitting to particular catchpits.
Where a bag is supported by a rigid frame it is bulky to transport and handle, uses much material to achieve rigidity, and can be difficult to install since many pits have differences in geometry or manufacturing flaws some times requiring a custom fit. The designs may also suffer from bulging of the filter bag which can block a pit outlet and place localised stress on the filter bag. In addition the bulging of the bag can cause it to be trapped in the frame or pit walls, to the extent it is not removable with out considerable effort or damage to the bag or frame. The designs may also suffer from small filter area and containment volume requiring a high frequency of maintenance. The designs may also be complex, expensive to manufacture and pose a potential fire risk.
It is an object of the invention to provide an improved storm water filter and components and methods of installation and use or to at least provide the public with a useful choice.
Reference to any prior art in this specification does not constitute an admission that such prior art forms part of the common general knowledge.